• 한국소음진동공학회논문집
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• 제15권7호
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• pp.806-812
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• 2005

This paper adresses the shaking table tests with 1/100 scaled model followed similitude law for OOdam main designing section to understand nonlinear behavior characteristics of concrete dam body by ground motion. As earthquake wave, Hachinohe and El Centre waves were used and acceleration and displacements are measured to analyze behaviors of dam body. For maximum ground acceleration range $(0.3\~0.9 g)$, the results showed linear behavior regardless of maximum 9round acceleration and secured safety of structure. To analyze the behavior of dam after tension cracking, 3 cm-notch was placed at the critical section of over-flowing section. As results of applying Hachinohe wave(0.8 g), Even though tension cracks were formed at over-flowing section by Hachinohe wave(0.8 g), it showed that the dam is stable for supporting upper stream Part of water tank of dam.

• Journal of electromagnetic engineering and science
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• 제10권4호
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• pp.322-327
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• 2010

Spaceborne sparse array radar for ground moving targets indication (GMTI) has outstanding advantage over full array radar for constructing ultra-large aperture. Rapid development of millimeter wave (MMW) technology make it possible for realizing MMW GMTI radar, which is much more sensitive to slow moving ground target. The paper presented the system model of a multi-carrier frequency sparse array MMW radar as well as preliminary simulation results, which showed future application of the system is very promising.

• 한국지진공학회논문집
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• 제18권2호
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• pp.73-78
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• 2014

In this paper, the stochastic 1D site response analysis method using Monte Carlo simulation and considering thespatial variation of shear wave velocity profile isproposed. To consider thespatial variation of shear wave velocity profile for 1D site response analysis, the proposed method generates random shear wave velocity profiles representing the target site, and Monte Carlo simulation is used to calculate theprobability distribution of the site response analysis results such as thepeak ground acceleration. Through the field application, The applicability of the proposed method is verified through field application.

• 산업기술연구
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• 제31권B호
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• pp.81-90
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• 2011

Centrifuge modeling and numerical analysis on works of breakwater construction were performed to investigate the behavior of caisson type of breakwater and foundation treated with the method of DCM (Deep Cement Mixing) under the condition of wave action in field. In centrifuge modeling, construction sequence of breakwater caisson such as preparation of ground, treatment of DCM, installation of rubble mound, placement of breakwater caisson and lateral loading on the breakwater due to wave action were reconstructed. Lateral movement of model breakwater and ground reaction in the vertical direction were monitored during test. Stress concentration ratio between the untreated ground and the treated ground with DCM was evaluated from measurement of vertical stresses on each ground. Numerical analysis with the software of PLAXIS was carried to compare with Results of centrifuge model test. It was found that stability of model breakwater was maintained during stage of construction and the compared results about stress concentration ratio were in relatively good agreements.

• Journal of electromagnetic engineering and science
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• 제15권2호
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• pp.120-122
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• 2015

This study presents a new, simple method for improving the front-to-back (F/B) ratio of a microstrip patch antenna (MSA) based on surface wave suppression. The back radiation of the MSA is significantly reduced by using the meandered ground plane edges and placing split-ring resonators (SRRs) in the middle of the meandered slots. By loading SRRs near the center of the meandered ground plane edges, some parts of the diffracted back-lobe power density can be reduced further. Compared to the F/B ratio of a conventional MSA with a full ground plane of the same size, an improved F/B ratio of 18 dB has been achieved experimentally for our proposed MSA.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.265-268
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• 2008

The safety of a tunnel under seismic motion is most often evaluated by ovalling deformation of tunnel. This paper research about tunnel's longitudinal deformation. Because of spatial variation of seismic ground motion, the longitudinal structures like tunnel are likely to experience relative displacements along longitudinal direction. The spatially variable ground motion can be estimated by coherency function obtained empirically, and can be considered from different arrival times of ground motion. As a result of estimating tunnel's relative displacements at maximum curvature of tunnel, the displacements and curvatures estimated by coherency function affect the tunnel's safety more than different arrival times. However, if tunnel's displacements by coherency function superpose on displacements by different arrival times, the relative displacements and curvatures of tunnel will be more severe. Therefore, to estimate accurately tunnel's deformation in longitudinal direction has to consider both coherency and wave passage effects.

• Structural Engineering and Mechanics
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• 제18권2호
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• pp.231-246
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• 2004

In this paper, a comparison of various random vibration and deterministic dynamic analyses of cable-stayed bridges subjected to asynchronous ground motion is presented. Different random vibration methods are included to determine the dynamic behaviour of a cable-stayed bridge for various ground motion wave velocities. As a numerical example the Jindo Bridge located in South Korea is chosen and a 413 DOF mathematical model is employed for this bridge. The results obtained from a spectral analysis approach are compared with those of two random vibration based response spectrum methods and a deterministic method. The analyses suggest that the structural responses usually show important amplifications depending on the decreasing ground motion wave velocities.

• Geomechanics and Engineering
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• 제30권5호
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• pp.449-460
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• 2022

Safe underground construction in a rock mass requires adequate ground investigation and effective determination of rock conditions. The estimation of rock mass behavior is difficult, because rock masses are innately anisotropic and heterogeneous at different scales and are affected by various environmental factors. Quantitative rock mass classification systems, such as the Q-system and rock mass rating, are widely used for characterization and engineering design. The measurement of rock classification parameters is subjective and can vary among observers, resulting in questionable accuracy. Geophysical investigation methods, such as seismic surveys, have also been used for ground characterization. Torsional shear wave propagation characteristics in cylindrical rods are equal to that in an infinite media. A probabilistic quantitative relationship between the Q-value and shear wave velocity is thus investigated considering long-wavelength wave propagation in equivalent continuum jointed rock masses. Individual Q-system parameters are correlated with stress-dependent shear wave velocities in jointed rocks using experimental and numerical methods. The relationship between the Q-value and the shear wave velocity is normalized using a defined reference condition. This relationship is further improved using probabilistic analysis to remove unrealistic data and to suggest a range of Q-values for a given wave velocity. The proposed probabilistic Q-value estimation is then compared with field measurements and cross-hole seismic test data to verify its applicability.

• 한국전자파학회논문지
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• 제25권9호
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• pp.944-951
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• 2014

본 논문에서는 위성의 지상국 위치를 선정함에 있어 전파 간섭을 피하고, 사용자의 위성활용도를 극대화하기 위한 지상국 위치 선정 전파 간섭 연구이다. 위성 지상국의 위치 선정을 위해 부지 확보가 용이하고, 평가지표의 평가항목별로 평가가 가능하다고 판단되는 지상국 후보지에 대해 전파 환경을 조사하고, 측정 결과를 제시하였으며, 10명의 전문가의 적합성 판단을 통해 후보지의 적합성에 대해 검토하였다. 향후 다른 후보지들의 측정 결과와 비교를 통해 최적의 지상국 위치를 선정할 수 있도록 하였다. 또한, 위성 지상국을 구축하고 있는 세계적 추세에 맞추어, 우리나라의 위성 지상국 위치 선정을 위한 정량적인 평가기준이 될 수 있다.

• 한국터널지하공간학회 논문집
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• 제15권1호
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• pp.13-24
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• 2013

현재 다양한 탄성파 기반의 물리탐사 기법들이 지반조사를 위해 널리 이용되고 있는데 이는 지반의 동적 특성들이 공학적 물성과 상관관계를 갖기 때문이다. 하지만, 지반공학적 물성치들의 고유한 비균질성이 탄성파 속도 및 진폭 등의 전파 특성에 영향을 미침에도 불구하고 그에 대한 고려가 안되고 있는 실정이다. 그래서, 본 연구에서는 지반의 고유한 비균질성이 탄성파 전파특성에 미치는 영향을 규명하기 위하여 추계론적 수치해석 방법을 적용하였다. 탄성파의 도달 시간 변화와 파두 특성에 주안점을 두어 분석을 수행하였다. 지반의 공간적 상관 거리와 파장과의 상관성 및 탄성파 전파거리와 파장과의 상관성이 탄성파의 도달 시간 변화에 미치는 영향에 대하여 조사하였다. Turning band method를 적용하여 변동계수의 범위가 10 ~ 40%인 다양한 비균질 강도를 갖는 지반을 유한차분 그리드에 생성하였다. 유한차분법을 이용하여 비균질 지반에서 탄성파의 전파를 시뮬레이션하였고, 추계론적 기법으로는 Monte Carlo 시뮬레이션 기법을 적용하였다. 추계론적 수치해석 결과, 지반의 비균질 강도가 증가함에 따라 탄성파의 파두 형상의 일그러짐이 현저하게 발생하였고, 그에 따라 탄성파의 도달 시간도 지연되는 것으로 나타났다. 지반의 공간적 상관 거리와 파장과의 상관성 및 탄성파 전파 거리와 파장과의 상관성은 탄성파의 도달 시간 변화와 긴밀한 상관성이 있는 것으로 나타났다.